what is the difference in ignition module from automatic and 5 speed...

 

Different part number. Does not interchange.

 

why do some companys just make one kind and then others make two different one???

 

well they didn't make as many aod mustangs at that time as they did 5 speed. i am sure it's not hard to find a module for an aod though. at least not a cheap one. you wanna try, and get a durable one though, because those modules can be a real pain in the ***.